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EVOLVING A RATIONAL TRANSIT SAFETY PROGRAM

The system safety principles and procedures developed by the U.S. Department of Defense are discussed with regard to their applicability to transit. Possible difficulties include the cost of implementing large-scale system analysis techniques, such as fault-free analysis, and the difficulty of obtaining reliable probability data for the various failure modes when completely new and unproven designs are considered. Notwithstanding these difficulties, there does not seem to be any inherent conflict between Department of Defense procedures and traditional railroad practices. In fact, the former specifically recommend that historical safety data from similar applications be integrated into the safety plan and that fail-safe design procedures be used to control high-risk situations. Two examples of how military risk management techniques can be combined with traditional rail practices are provided. The first is a preliminary hazard analysis, and the second shows how fault-tree techniques can be used to investigate whether a brick-wall stopping criterion is really necessary. /Author/